FIG. 8A is a top view of a conventional automobile frame component. FIG. 8B is a cross-sectional view of the automobile frame component. FIG. 9 is an enlarged view of part A illustrated in FIG. 8B. In general, as illustrated in FIG. 8B, an automobile frame component is manufactured so as to constitute a closed section by welding a frame component 3 that includes a flange portion 3a and has a substantially hat-like sectional shape to another frame component or a panel part 5. Such an automobile frame component 11 has conventionally been manufactured by joining the flange portion 3a of the frame component 3 to the other frame component or the panel part 5 using resistance spot welding.
In the resistance spot welding (hereinafter, spot welding), the diameter of spot welding electrodes need to be large, and the electrodes need to be pressed vertically against the flange portion 3a. For this reason, a product is provided with the flange portion 3a having a width of roughly 25 mm, and the flange portion 3a is joined to the other frame component or the panel part 5 by welding the central part of the width.
In contrast, by using continuous welding, such as laser welding or laser-arc hybrid welding which combines laser welding with consumable electrode type arc welding, it is possible to weld a boundary position (contact end between the flange portion 3a and the panel part 5) between the flat flange portion 3a and a circular arc-like portion 3c continuing to a vertical wall portion 3b. 
Patent Literature 1 describes a technique that uses laser-arc hybrid welding to apply continuous welding to a position in a range of less than 1.5 mm from the contact end between the flange portion 3a and the panel part 5 toward the vertical wall portion 3b (toward the circular arc-like portion 3c).